Intel SL2YM User Manual
Pentium
®
II Processor at 350 MHz, 400 MHz, and 450 MHz
Datasheet
11
2.2
Clock Control and Low Power States
Pentium II processors allow the use of AutoHALT, Stop-Grant, Sleep, and Deep Sleep states to
reduce power consumption by stopping the clock to internal sections of the processor, depending
on each particular state. See
reduce power consumption by stopping the clock to internal sections of the processor, depending
on each particular state. See
Figure 3
for a visual representation of the Pentium II processor low
power states.
Figure 2. AGTL+ Bus Topology
Pentium
®
II
Processor
ASIC
Pentium II
Processor
ASIC
Figure 3. Stop Clock State Machine
PCB757a
2. Auto HALT Power Down State
BCLK running.
Snoops and interrupts allowed.
Snoops and interrupts allowed.
HALT Instruction and
HALT Bus Cycle Generated
HALT Bus Cycle Generated
INIT#, BINIT#, INTR,
SMI#, RESET#
SMI#, RESET#
1. Normal State
Normal execution.
STPCLK#
Asserted
Asserted
STPCLK#
De-asserted
De-asserted
3. Stop Grant State
BCLK running.
Snoops and interrupts allowed.
Snoops and interrupts allowed.
SLP#
Asserted
Asserted
SLP#
De-asserted
De-asserted
5. Sleep State
BCLK running.
No snoops or interrupts allowed.
No snoops or interrupts allowed.
BCLK
Input
Stopped
Input
Stopped
BCLK
Input
Restarted
Input
Restarted
6. Deep Sleep State
BCLK stopped.
No snoops or interrupts allowed.
No snoops or interrupts allowed.
4. HALT/Grant Snoop State
BCLK running.
Service snoops to caches.
Service snoops to caches.
Snoop Event Occurs
Snoop Event Serviced
Snoop
Event
Occurs
Event
Occurs
Snoop
Event
Serviced
Event
Serviced
STPCLK# Asserted
STPCLK# De-asserted